CT scan is complementary to MRI in

(C) Posterior fossa tumour# Skull base anatomy is complex. Numerous vital neurovascular structures pass through multiple channels and foramina located in the base skull. With the advent of computerized tomography (CT) and magnetic resonance imaging (MRI), accurate preoperative lesion localization and evaluation of its relationship with adjacent neurovascular structures is possible.> It is imperative that the radiologist and skull base surgeons are familiar with this complex anatomy for localizing the skull base lesion, reaching appropriate differential diagnosis, and deciding the optimal surgical approach.> CT and MRI are complementary to each other and are often used together for the demonstration of the full disease extent> Diagnosis of Posterior Fossa Tumor is based on a thorough medical history and physical examination, followed by imaging tests. The best way to look at the posterior fossa is with an MRI scan. CT scans are usually not helpful to see that area of the brain.> CT scan is very much useful in traumatic lesions.> Hydrocephalus is best diagnosed by MRI scan and even Plain X-ray.